Assessing the Application Effects and Operating Conditions on Three Different Insulation Capacity Walls Using Internal Quantitative Infrared Thermography in China

Quantitative infrared thermography (QIRT) has emerged as a prominent topic within the field of thermal performance testing of building enclosures. The majority of the previous research has been conducted in Europe and North America, with limited research activity in Asia. Against the backdrop of China’s carbon emission reduction goals, quantitative infrared thermography offers a promising avenue for advancing building energy efficiency testing. This study conducted QIRT testing on three buildings with different insulation capabilities (old buildings, conventional insulated buildings, nearly zero-energy buildings) in Shenyang, China. The objective was to assess the efficacy of the internal QIRT method for walls with varying insulation capabilities and to ascertain the requisite testing environment parameters in the context of China’s climatic conditions and building regulations. The heat flow meter method was employed to verify its accuracy. Furthermore, correlation analysis was conducted on various testing parameters across different building cases and temperature-difference ranges. The results indicate that walls with different insulation capabilities require corresponding indoor–outdoor temperature differentials to establish a stable heat flow environment. For uninsulated buildings, a temperature difference of 10 °C between indoor and outdoor environments is sufficient to meet testing requirements, with a testing error of only 2.28%. For conventionally insulated buildings, a temperature difference greater than 20 °C reduces the relative error to below 10%. For nearly zero-energy buildings, it is recommended to maintain a temperature difference of 25 °C or higher to achieve optimal testing results. Once a stable thermal flow environment has been achieved, the variation in the instantaneous heat transfer coefficient maintains a high correlation with the temperatures recorded at various measurement points. For buildings with high insulation performance, high temperature-difference environments pose higher demands on the testing procedures and data collection using the QIRT method. During the testing process, it is essential to monitor changes in outdoor air temperature, enhance the accuracy of infrared thermography, and avoid interference from indoor radiation sources.

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